We are requesting funds to purchase a next generation, user-operated Fluorescent Activated Cell Sorter that will both increase the cell sorting capacity at UCSF and update the capability of our current cell sorters in the Parnassus Flow Cytometry Core (PFCC). We have selected the Becton Dickenson FACSAria Fusion as the instrument that best fulfills the needs of our NIH-funded faculty. This cell sorter exceeds the PFCC's most sophisticated core-operated systems while maintaining ease of use; has biosafety and aseptic features that meet an increasing demand for sorting primary human cells and will enable UCSF researchers to directly sort and collect cells at high speeds with flexible configurations. Purchase of a FACSAria Fusion for the PFCC will provide maximal benefit to the entire, NIH-funded research enterprise at UCSF. Currently, each user-operated cell sorter in our shared resource facility averages 40 hours of use per week, severely limiting availability for new projects and for sorting of human clinical samples that are often obtained on short notice. High-speed cell sorting has become an essential tool in many fields, particularly immunology, developmental biology, cancer, and stem cell biology; and limited access to multiparameter high-speed cell sorting at UCSF, particularly on the Parnassus campus, has become a bottleneck for research progress. This limitation in cell sorting capacity impacts many investigators in numerous departments and research areas, new and early- career investigators are particularly hard-hit. In this application, we have identified 22 Investigators (19 major and 3 minor users, with 20 users funded by NIH grants) whose 27 research projects require increased access to cell sorting, as well as the specific capabilities of the FACSAria Fusion that are not provided by older Cell Sorters in our facility. Based on our evaluation of the needs of these investigators and availability of sorters and their configurations at the Parnassus campus of UCSF, we have decided to request a new BD FACSAria Fusion sorter with the configuration detailed in the equipment section. The choices on the make, model, and configuration, and operational plans are designed to complement existing sorters and maximally benefit investigators defined in this application as well as the entire research community at UCSF.